Wireless communication device and wireless communication method

ABSTRACT

The present invention relates to a wireless communication device performing communications by using a radio frame containing a control channel and a data channel, the wireless communication device comprises of a structuring unit that allocates a first part of the control channel adjacent to the data channel in the radio frame, and allocates a second part of the control channel, which denotes different control information from the first part, to the data channel so as to be inserted between data of the data channel and a transmission unit that transmits the radio frame including the data channel and the control channel.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a divisional of U.S. application Ser. No.11/487,352, filed on Jul. 17, 2006, now pending, which claims thebenefit of Japanese Patent Application No.JP2006-069037, filed on Mar.14, 2006, the contents of each are herein wholly incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless communication device and awireless communication method that perform communications by use of awireless frame containing a control channel and a data channel.

2. Description of the Related Art

In a cellular mobile communication system, cells as communication areascovered by respective base stations are located so as to be neighboringto each other or partially overlapped with each other. Each base stationconnects each mobile station to the mobile communication system byperforming wireless communications with a plurality of mobile stationslocated within each corresponding cell. In this type of cellular mobilecommunication system, an important subject is to improve a throughput inthe mobile station located at the cell edge. Generally, an error ratecharacteristic deteriorates in the cell edge, because the received powerfrom the base station covering the cell is attenuated, and the mobilestation is susceptible to interference by the signals from the basestations located in other cells in the periphery.

A method of solving such a problem is a method of giving, as fortransmission signals to the mobile station at the cell edge, more ofredundancy of the data than the transmission signals to other mobilestations. This is the method of transmitting the data repeatedlyinserting the information having the same content with respect to thetransmission signals to the mobile station at the cell edge. Thismethod, however, causes the transmission frame to be upsized and leadsto an increase of an overhead of the transmission frame. Further, evenwhen fixing a transmission frame length, it follows that a substantialdata transmission quantity decreases.

Another method is that the transmission data to the mobile station atthe cell edge is subjected to error correction coding that exhibits thehigher redundancy than the transmission data to other mobile stations.Proposed in regard to this method is a scheme (refer to Non-Patentdocument 1) that turbo encoding having a one-third (⅓) coding rate isused for the transmission data to the mobile station in the vicinity ofthe base station, and the low-rate turbo encoding having the codingrates such as ⅕ and 1/9 that are equal to or lower than ⅓ is used forthe transmission data to the mobile station at the cell edge (refer to“3rd Generation Partnership Project, “Lower rate extension of channelcoding to the rate<⅓”, 3GPP TSG RAN WG1 meeting #42bis (R1-051082),2005-10, Agenda Item 8.7.”). With this scheme, even in thecommunications to the mobile station located at the cell edge in atransmission environment of very poor quality, it is expected to preventthe deterioration in the error rate characteristic and the decrease inthe throughput by using the low-rate turbo encoding with the increasedredundancy.

In the conventional arts described above, however, though capable ofimproving the decrease in the throughput with respect to a data channelfor transmitting to the mobile station located at the cell edge, aproblem about the transmission of a control channel still remains. Thisproblem will hereinafter be explained with reference to FIGS. 14, 15 and16. FIG. 14 is a diagram showing a frame format used for theconventional cellular mobile communication system. FIG. 15 is a diagramshowing a coding switchover method corresponding to a cell location inthe prior art. FIG. 16 is a diagram showing a transmitting/receivingstate in the prior art.

The frame format as shown in FIG. 14 is used for the communicationsbetween the base station and the mobile station. The wireless frame isassembled by a pilot channel (PICH), a control channel (CCH) and a datachannel (DCH). The coding switchover method proposed in the conventionalart described above is a technique targeting on the data channel in thewireless frame. Generally, as for the control channel, convolutionalcoding having the coding rate “⅓” is used in common with the respectivemobile stations.

FIG. 15 shows an example of such a case that a base station 500 coveringa cell 510 performs the communications with a mobile station 501 locatedin the vicinity of the base station 500 and with a mobile station 502located at the cell edge. In the conventional art, 16 QAM (QuadratureAmplitude Modulation) modulation method and the turbo encoding havingthe coding rate “⅓” are used for the data channel in the signals to themobile station 501 located in the vicinity of the base station 500, andQPSK (Quadrature Phase Shift Keying) modulation method and theconvolutional coding having the coding rate “⅓” are used for the controlchannel. Such a design is made that the transmission of the controlchannel totally exhibits a more preferable error rate characteristicthan by the transmission of the data channel in the vicinity of the basestation 500.

On the other hand, the communications with the mobile terminal 502located at the cell edge involve such a change that the QPSK modulationmethod and the low-rate turbo encoding with its coding rate equal to orlower than the coding rate “⅓” are used for the data channel, andinvolve using, for the control channel, the QPSK modulation method andthe convolutional coding having the coding rate “⅓” as they are. Namely,in the mobile station located at the cell edge, the data channel usesthe coding having the larger redundancy than the control channel has,and therefore such a phenomenon might occur that the error ratecharacteristic of the control channel becomes lower than the error ratecharacteristic of the data channel at the cell edge.

In the conventional arts, the control channel contains controlinformation for correctly demodulating and decoding user data allocatedto the data channel, and hence, as shown in FIG. 16, if the mobilestation 502 detects that an error occurs in the control channel, themobile station 502 prompts the base station 500 to executeretransmission. Accordingly, in the conventional arts, it follows thatthe retransmission is repeated if the error frequently occurs in thecontrol channel and that a decrease in transmission efficiency of thewhole system is brought about.

For solving these problems, it is considered that the redundancy of thecoding used for the control channel is set larger than the codingredundancy for the data channel. In this method, however, the controlchannel generally uses a format common to all the mobile stations, andtherefore, when increasing the redundancy for the control channel andupsizing the control channel, it follows that the whole transmissionframe gets excessively upsized. Further, even when fixing thetransmission frame length, it follows that the substantial transmissionquantity decreases due to the increase in the overhead of the controlchannel. Hence, this type of method results in increasing the overheadof the transmission frame.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a wirelesscommunication device and a wireless communication method that improve athroughput without increasing the overhead of the wireless frame.

The present invention adopts the following configurations in order tosolve the problems described above. Namely, according to the presentinvention, a wireless communication device performing communications byusing a wireless frame containing a control channel and a data channel,comprises a structuring unit allocating, as second control information,part of control information used for communication control to the datachannel with respect to a transmitted wireless frame to be transmittedto one other wireless communication device.

Given herein as the control information used for the communicationcontrol are, for example, information on a modulation method, a codingrate etc about the wireless frame to be transmitted, and informationsuch as CQI (Channel Quality Information), a modulation method and acoding rate that should be utilized for the wireless frame to betransmitted to the present wireless communication device from the otherwireless communication device as a transmission destination. In thepresent invention, there is transmitted the wireless frame in which partof these control information is allocated as the second controlinformation to the data channel.

Hence, according to the present invention, in the wireless communicationdevice receiving the transmitted wireless frame, even if an error occursin the received control channel, without making a retransmissionrequest, the control information, which might have been utilized if theerror would not occur, is estimated, and the user data can bedemodulated and decoded by using this estimated control information.

With this scheme, according to the present invention, without increasingan overhead of the wireless frame, even in the case of performing thecommunications with the mobile station in a channel status of whichquality is as poor as in the vicinity of a cell edge, it is possible toreduce the retransmission due to occurrence of the error in only thecontrol channel and to improve the throughput.

Further, the wireless communication device according to the presentinvention may further comprise a rate determination unit determining,based on information of a channel status with a wireless communicationdevice as a transmission destination, redundancy of the data channelwith respect to the transmitted wireless frame, wherein the structuringunit, when the determined redundancy of the data channel becomes higherthan redundancy of the control channel, may allocate the second controlinformation to the data channel.

In the present invention, the redundancy of the data channel of thetransmitted wireless frame is changed based on the information of thechannel status with the wireless communication device as thetransmission destination. Then, as a result of being changed, if theredundancy of the data channel gets higher than the redundancy of thecontrol channel, the second control information is allocated to the datachannel.

Accordingly, in the present invention, for instance, if poor of thechannel status with the other wireless communication device as thecommunication partner device and if increasing the redundancy of thedata channel, the second control information is allocated to the datachannel and is, whereas if not, allocated to the control channel asconventional.

With this scheme, the proper wireless frame can be used corresponding tothe channel status while improving the throughput by reducing theretransmission, and the extra overhead of the wireless frame can bereduced.

Moreover, in the wireless communication device according to the presentinvention, the structuring unit may dually allocate the second controlinformation to the control channel and to the data channel.

Further, in the wireless communication device according to the presentinvention, the structuring unit may allocate, as first controlinformation, in the control information, the information used for thedemodulation process and for the decoding process in the wirelesscommunication device receiving the transmitted wireless frame to thecontrol channel, and may set other information as the second controlinformation.

In the present invention, in the wireless communication device receivingthe transmitted wireless frame, the easy-to-estimate information isallocated to the control channel, and other hard-to-estimate informationare allocated to the data channel.

Hence, according to the present invention, in the wireless communicationdevice on the receiving side, if the error occurs in only the controlchannel, the data allocated to the data channel can be demodulated anddecoded by using the control information to be estimated, and thereforethe occurrence of the retransmission can be further reduced.

Still further, in the wireless communication device according to thepresent invention, the structuring unit, with respect to the transmittedwireless frame, may set, as the second control information, the controlinformation related to the received wireless frame in the controlinformation.

Herein, in the control information, the control information for thewireless frame received from the other wireless communication device is,for example, the CQI and is exemplified such as a modulation methodindicated to the other wireless communication device by the presentwireless communication device. These information are thehard-to-estimate information in the wireless communication devicereceiving the wireless frame, and are allocated to the data channel.

With this scheme, according to the present invention, even if the erroroccurs in the control channel, the other wireless communication devicecan generate the transmitted wireless frame by using the second controlinformation allocated to the data channel, and it is therefore possibleto reduce the occurrence of the retransmission.

Yet further, according to the present invention, a wirelesscommunication device performing communications by using a wireless framecontaining a control channel and a data channel, comprises an errordetection unit detecting an error in data allocated to the receivedcontrol channel, an estimating unit estimating the control informationthat should be allocated to the received control channel, and ademodulating/decoding unit demodulating and decoding, if an error isdetected by the error detection unit, the data allocated to the receiveddata channel by using the control information estimated by theestimating unit.

The wireless communication device according to the present inventionspecifies a configuration of the wireless communication device on theside of receiving the wireless frame transmitted by the wirelesscommunication device described above. Namely, if the error occurs in thedata allocated to the control channel, since this data allocated to thecontrol channel can not be used, the data allocated to the received datachannel is demodulated and decoded based on the control informationestimated by the estimating unit.

Moreover, the wireless communication device according to the presentinvention may further comprise a generation unit extracting the controlinformation contained in the data demodulated and decoded by thedemodulating/decoding unit, and generating respective pieces of dataallocated to the control channel and the data allocated to the datachannel by use of the extracted control information with respect to thetransmitted wireless frame that should be transmitted.

According to the present invention, even if the error occurs in thecontrol channel, the transmitted wireless frame can be generated byusing the control information in the data channel, and hence theoccurrence of the retransmission can be reduced.

It should be noted the present invention may also be a program foractualizing any one of the functions described above. Further, thepresent invention may also be a readable-by-computer storage mediumstored with this program.

According to the present invention, it is possible to actualize thewireless communication device and the wireless communication method thatimprove the throughput without increasing the overhead of the wirelessframe.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an example 1 of a frame format in theembodiment;

FIG. 2 is a diagram showing an example 2 of the frame format in theembodiment;

FIG. 3 is a diagram showing a transmitting/receiving state in theembodiment;

FIG. 4 is a diagram showing a frame format in a first embodiment;

FIG. 5 is a diagram showing a device configuration of a base station inthe first embodiment;

FIG. 6 is a diagram showing an example of an MCS table;

FIG. 7 is a diagram showing a device configuration of a mobile stationin the first embodiment;

FIG. 8 is a diagram showing a receiving operation of the mobile stationin the first embodiment;

FIG. 9 is a diagram showing a frame format (a case of not conductingin-band) in a second embodiment;

FIG. 10 is a diagram showing a frame format (a case of conducting thein-band) in the second embodiment;

FIG. 11 is a diagram showing the device configuration of the basestation in the second embodiment;

FIG. 12 is a diagram showing the device configuration of the mobilestation in the second embodiment;

FIG. 13 is a diagram showing an example of the receiving operation ofthe mobile station in the second embodiment;

FIG. 14 is a diagram showing a conventional frame format;

FIG. 15 is a diagram showing a coding switchover method in accordancewith a conventional cell location; and

FIG. 16 is a diagram showing a transmitting/receiving state in the priorart.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Outline of Embodiments of theInvention

For discussing embodiments of the present invention, at first, anoutline of the embodiments of the present invention will be explainedwith reference to FIGS. 1 and 2. FIGS. 1 and 2 are diagrams showing anexample of a transmission frame format used in the embodiments of thepresent invention. In the embodiments, control information allocated toa control channel in the frame format shown in FIG. 14 is segmented intotwo parts (a control information part 1 and a control information part2), wherein the control information part 2 thereof is allocated to adata channel.

As a method of segmenting the control information, there is considered amethod by which the control information part 2 contains such a piece ofinformation as to be changed each time performing the transmission andunable to be easily estimated in a receiving-side device, while thecontrol information part 1 contains other pieces of information that canbe easily estimated in the receiving-side device. Specifically, forinstance, the information about a modulation method, a coding rate, etcis contained in the control information part 1, and the information suchas CQI (Channel Quality Information) representing a channel status iscontained in the control information part 2. This is because theinformation about the modulation method supported by a system to someextent, which is fixed as in the case of QPSK (Quadrature Phase ShiftKeying) and 16 QAM (Quadrature Amplitude Modulation), is data that fallswithin a fixed range even when changed and is therefore considered to bethe data easy to be estimated in the receiving-side device, while theinformation such as the CQI is data that momentarily changes and isunfixed in width of this change and is therefore considered not to bethe data that can be easily estimated in the receiving-side device.

Considered is an example where the thus-segmented control informationpart 1 and control information part 2 are allocated as shown in FIGS. 1and 2. FIG. 1 shows an example in which the control information part 2is allocated dually to the control channel and to the data channel. FIG.2 shows an example in which the control channel contains only thecontrol information part 1, and the control information part 2 isallocated to the data channel. In the example shown in FIG. 2, a lengthof the control channel is shorter than a length of the conventionalcontrol channel illustrated in FIG. 14.

FIG. 3 is a diagram showing a transmitting/receiving state in theembodiment using the frame format as described above. In thetransmitting/receiving state in the case of the conventional art shownin FIG. 16, if an error occurs in the control information, thereceiving-side device requests a transmitting-side device to retransmitwithout decoding user data; and, in the transmitting/receiving state inthe embodiment shown in FIG. 3, even if the error occurs in the controlinformation, a possibility that the user data is correctly demodulatedand decoded is improved by estimating the control information part 1.

In a case where a mobile station is located in the vicinity of a basestation and so on, however, in such an environment that the controlchannel has a more preferable error rate characteristic than the datachannel has, there is no merit in allocating a part of the controlchannel to the data channel, and hence the conventional message formatshown in FIG. 14 should be employed. In the embodiment, the frame formatis changed over corresponding to respective coding rates used in thedata channel and in the control channel. To be specific, if the codingrate of the data channel exhibits higher redundancy than the coding rateof the control channel, the control information part 2 is allocated tothe data channel, and, whereas if the coding rate of the data channelexhibits the lower redundancy than the coding rate of the controlchannel, the conventional frame format is used. In the followingdiscussion, a scheme of allocating the control information part 2 to thedata channel is referred to also as [conducting the in-band].

First Embodiment

A wireless communication system in a first embodiment of the presentinvention will hereinafter be described with reference to the drawings.Configurations in the following embodiments are exemplifications, andthe present invention is not limited to the configurations in theembodiments.

System Architecture

The wireless communication system in the first embodiment shall be, asshown in FIG. 15, configured by a base station device (which willhereinafter simply be termed a base station) 500, and a mobile stationdevices (which will hereinafter be simply termed mobile stations) 501and 502. The configuration illustrated in FIG. 15 is nothing more thanone example adopted for the sake of explanatory convenience, wherein aplurality of base stations and a plurality of mobile stations may exist,and an unillustrated control device etc may further be provided.Hereinafter, as shown in FIG. 15, the explanation will be made alongwith such a case example that the base station 500 covering a cell 510performs communications respectively with the mobile station 501 locatedin the vicinity of the base station 500 and with the mobile station 502located at the cell edge.

Frame Format

The frame format used in the wireless communication system in the firstembodiment will be explained with reference to FIG. 4. FIG. 4 is adiagram showing the frame format in the first embodiment, and shows theformat of a frame (a frame of a downlink) to be transmitted from thebase station 500 to the mobile station 501 or 502. The frame format inthe first embodiment corresponds to the example shown in FIG. 1, whichhas been described in the item of the Outline of Embodiment of theInvention, and has a structure wherein the control information part 2 isdually allocated to the control channel (CCH) and to the data channel(DCH).

In the first embodiment, the control information is segmented in a waythat sets downlink control information as the control information part 1(PART 1) and uplink control information as the control information part2 (PART 2). The downlink control information contains a modulationmethod, a coding rate, a data length, etc that are related to the datatransmitted in the form of the frame. On the other hand, the uplinkcontrol information contains the CQI estimated by the base station, themodulation method and the coding rate that are indicated to the mobilestation by the base station and a result of a cyclic redundancy check(which will hereinafter be abbreviated to CRC) of a transmission messageto the base station from the mobile station.

The uplink control information segmented as the control information part2 is, it follows, allocated to the data channel. In-band information(IN-BAND) is further allocated to the data channel. A reason why thisin-band information is allocated to the data channel lies in keeping acontrol channel size unchanged. The data channel size can be judged fromthe data length contained in the downlink control information, andtherefore no problem arises even when the in-band information is thusallocated thereto.

The in-band information contains presence/absence information showingwhether the control information part 2 is allocated to the data channelor not (presence or absence of the in-band) and allocation informationshowing a location where the control information part 2 in the datachannel is allocated. A piece of identifying information expressed by,e.g., a numerical value may be set in the presence/absence informationfield, wherein such a scheme may be taken that when [0] is set, thisrepresents no existence of the control information part 2, and, when [1]is set, this represents existence of the control information part 2. Anoffset address from, e.g., the head of the data channel may also be setin the allocation information field.

It should be noted the data contained in the control information part 1and the control information part 2 are not limited to the data describedabove, and the data structure thereof changes corresponding to thesystem. For instance, a spreading ratio, a code multiplexing count, etccan be contained as the downlink control information in a CDMA (CodeDivision Multiple Access) system, an antenna count etc can be containedas the downlink control information in a MIMO (Multi Input Multi Output)system, and a guard interval length etc can be contained as the downlinkcontrol information in an OFDM (Orthogonal Frequency DivisionMultiplexing) system. Further, in the case of a system where thetransmitting-side device computes reception timing of a signal from eachof the receiver devices and indicates transmission timing of thereceiving-side device corresponding thereto, information such as atiming adjustment notifying bit for actualizing this scheme can becontained as the uplink control information.

Base Station

A device configuration of the base station 500 in the first embodimentwill hereinafter be described with reference to FIG. 5. FIG. 5 is ablock diagram showing the device configuration related to transmittingfunctions of the base station 500 in the first embodiment. The basestation 500 in the first embodiment includes, as the transmittingfunctions, a pilot generation unit 101, a control information part 1generation unit 102, a control information part 2 generation unit 103, adata generation unit 104, a data structuring unit 105, a modulation unit106, a control information making unit 107, a modulation unit 108, amultiplexing unit 109, a transmission unit 110, a transmitting antenna115, a receiving antenna 115, a reception unit 121, an uplinktransmission frame decoding unit 122, a rate determining unit 123, achannel estimating unit 124 and a CQI information generation unit 125.Among these components, the receiving antenna 120, the reception unit121 and the uplink transmission frame decoding unit 122 are, thoughtaking a charge of the receiving functions, taken up herein as thefunctional units that acquire the information to be utilized in thefunctional units taking the transmitting functions.

The reception unit 121, upon receiving the signals transmitted from themobile station and received by the receiving antenna 120, executesprocesses such as a frequency conversion, an analog/digital conversionand demodulation upon the received signals. The reception unit 121 sendsthe signals, which have undergone these predetermined processes, to theuplink transmission frame decoding unit 122. Further, the reception unit121 sends a pilot signal in the receiving signals to the channelestimating unit 124.

The channel estimating unit 124 compares the pilot signal transferredfrom the reception unit 121 with an already-known pilot signal, therebyobtaining a channel estimation value related to the uplink to the basestation from the mobile station as a sender. This channel estimationvalue may also be obtained from, e.g., calculation by the least-squaresmethod. The present invention does not limit this channel estimatingmethod. This channel estimation value is transferred to the uplinktransmission frame decoding unit 122 and the CQI information generationunit 125.

The uplink transmission frame decoding unit 122 demodulates and decodesthe signals received from the reception unit 121 by use of the channelestimation value received from the channel estimating unit 124, andacquires the CQI transmitted from the mobile station as a signal senderof these signals from the decoded signals. The thus-acquired CQI istransferred to the rate determining unit 123.

The CQI information generation unit 125 generates the CQI related to theuplink based on the channel estimation value etc transferred from thechannel estimating unit 124. This CQI may also be generated and acquiredby dividing, for example, with respect to SINR (Signal to Interferenceand Noise Ratio), desired power of each symbol (“S”) by interferencenoise power (“I”). The desired power of each symbol is obtained bysquaring, e.g., an absolute value of the channel estimation value, andthe interference noise power is obtained by taking, e.g., a correlationbetween the receiving signal and the pilot signal. It is to be notedthat the present invention does not limit these CQI calculation methods.The uplink-related CQI generated by the CQI information generation unit125 is transferred to the rate determining unit 123.

The rate determining unit 123 receives the CQI transferred from theuplink transmission frame decoding unit 122, i.e., the downlink-relatedCQI generated in the mobile station and the CQI transferred from the CQIinformation generation unit 125, i.e., the uplink-related CQI generatedin the base station, and determines the predetermined coding rate andmodulation method on the basis of these CQIs. The rate determining unit123 determines the coding rate and the modulation method of the datachannel to be transmitted on the basis of the SINR contained in, e.g.,the downlink-related CQI, and determines the coding rate and themodulation method to be contained in the uplink control information onthe basis of the SINR contained in the uplink-related CQI.

The rate determining unit 123 previously retains an MCS (ModulationCoding Scheme) table as shown in FIG. 6, and determines the coding rateand the modulation method of the data channel by referring to this MCStable. FIG. 6 shows an example of the MCS table, wherein the SINR isassociated with the MCS. This is the table example in a case where theCQI transmitted from each of the mobile stations is the SINR. Anidentification number related to combination of the modulation methodand the coding rate is set in an MCS field.

The rate determining unit 123, when the SINR is transmitted as the CQIfrom the uplink transmission frame decoding unit 122, refers to the MCStable and thus determines the MCS associated with this SINR. Forexample, if the SINR is 3.5 decibels (dB), the rate determining unit 123selects MCS=2. This selection leads to such determination that themodulation method of the data channel is QPSK and the coding rate is ¾.The thus determined modulation method and coding rate of the datachannel are sent to the data structuring unit 105 and to the controlinformation part 1 generation unit 102.

The rate determining unit 123 similarly determines, based on theuplink-related CQI transferred from the CQI information generation unit125, the modulation method and the coding rate that should be indicatedto the mobile station by referring to the MCS table. The determinedmodulation method and coding rate are transferred, together with the CQItransferred from the CQI information generation unit 125, to the controlinformation part 2 generation unit 103. It should be noted that thefirst embodiment has exemplified the example of determining themodulation method etc on the basis of the SINR contained in the CQI,however, the determination thereof may also be made using CQIs otherthan this CQI.

The pilot generation unit 101, the control information part 1 generationunit 102, the control information part 2 generation unit 103 and thedata generation unit 104 are provided corresponding to the frame formatused in the first embodiment, and generate pieces of data in charge ofthese respective units. To be specific, the control information part 1generation unit 102 generates the downlink control information on thebasis of the downlink-related modulation method and decoding methodtransferred from the rate determining unit 123. The control informationpart 2 generation unit 103 generates the uplink control information onthe basis of the uplink-related modulation method and decoding methodtransferred from the rate determining unit 123 and also theuplink-related CQI transferred from the CQI information generation unit125. Herein, the CQI contained in the uplink control informationgenerated by the control information part 2 generation unit 103 containsthe uplink-related CQI generated by the CQI information generation unit125. Note that the CQI contained in the uplink control information mayalso contain the CQI generated by the mobile station and extracted bythe uplink transmission frame decoding unit 122.

The pilot data generated by the pilot generation unit 101 is transferredto the multiplexing unit 109, the control information part 1 (thedownlink control information) generated by the control information part1 generation unit 102 is transferred to the control information makingunit 107, the control information part 2 (the uplink controlinformation) generated by the control information part 2 generation unit103 is transferred respectively to the control information making unit107 and to the data structuring unit 105, and the user data generated bythe data generation unit 104 is transferred to the data structuring unit105.

The control information making unit 107 assembles the controlinformation part 1 and the control information part 2 together and thusgenerates control information data to be allocated to the controlchannel in the frame format shown in FIG. 4. The control informationmaking unit 107 encodes this control information data at a predeterminedcoding rate. The coding rate and the coding method implemented by thecontrol information making unit 107 involve using a coding rate and acoding method that are fixed in the system, wherein, for instance, aconvolutional coding method using a coding rate “⅓” is employed. Theencoded control information data undergoes the predetermined modulationprocess by the modulation unit 108 and is transferred to themultiplexing unit 109. The modulation method implemented by themodulation unit 108 involves using a method fixed in the system,wherein, for example, the QPSK is employed. Note that the coding rate,the coding method and the modulation method related to the controlchannel involve the use of the methods fixed in the system and may alsobe adjustably retained in a table etc. Moreover, the present inventiondoes not limit the coding rate, the coding method and the modulationmethod related to the control channel.

The data structuring unit 105 generates the data to be allocated to thedata channel in the frame format shown in FIG. 4. Hereat, the datastructuring unit 105 compares the coding rate of the data channel thatis received from the rate determining unit 123 with the coding rate ofthe control channel that is fixed in the system, thereby determiningwhether or not the control information part 2 received from the controlinformation part 2 generation unit 103 is allocated to the data channel.Specifically, the data structuring unit 105, if the coding rate of thedata channel is lower than the coding rate of the control channel,allocates the control information part 2 to a predetermined location inthe data channel, and, in cases other than this, does not allocate thecontrol information part 2 to the data channel.

The data structuring unit 105, in the case of allocating the controlinformation part 2 to the data channel, attaches the in-bandinformation, which [presence] set in the presence/absence informationfield and the allocation of the control information part 2 set in theallocation information field, to the head of the data to be allocated tothe data channel. The data structuring unit 105, if the controlinformation part 2 is not allocated to the data channel, attaches thein-band information which [absence] set in the presence/absenceinformation field and the initial value set in the allocationinformation field. The thus-generated data is coded at the coding ratetransferred from the rate determining unit 123 and is transferred to themodulation unit 106. The coding method implemented by the datastructuring unit 105 involves using the method fixed in the system,wherein normally a turbo encoding method is employed. The coded data ismodulated by the modulation unit 106 in a way that uses the modulationmethod determined by the rate determining unit 123, and is transferredto the multiplexing unit 109.

The multiplexing unit 109 multiplexes the pilot signal, the controlinformation signal and the data signal, which have been each modulated,and transfers these multiplexed signals to the transmission unit 110.The multiplexed signals transferred to the transmission unit 110 aresubjected to the processes such as the digital/analog conversion and thefrequency conversion, and are transmitted from the transmitting antenna115.

Mobile Station

A device configuration of each of the mobile stations 501 and 502 in thefirst embodiment will hereinafter be described with reference to FIG. 7.FIG. 7 is a block diagram showing the device configuration related toreceiving functions of the mobile stations 501 and 502 in the firstembodiment. Note that the mobile stations 501 and 502 are each the samedevice, and hence the following discussion shall deal with the mobilestation 501. The mobile station 501 in the first embodiment includes, asthe receiving functions, a receiving antenna 130, a demultiplexing unit132, a demodulation unit 133, a data decoding unit 134, an errordetection unit 135, a demodulation unit 136, a control informationselecting unit 138, an error detection unit 139, a channel estimatingunit 141, a control information estimating unit 142, a CQI informationgeneration unit 143, an uplink transmission frame generation unit 148, atransmission unit 149 and a transmitting antenna 150. Among thesecomponents, the transmitting antenna 150, the transmission unit 149 andthe uplink transmission frame generation unit 148 are, though taking acharge of the transmitting functions, taken up herein as the functionalunits for notifying the base station 500 of the CQI.

The receiving unit 131, upon receiving the signals transmitted from thebase station 500 and received by the receiving antenna 130, executes theprocesses such as the frequency conversion and the analog/digitalconversion upon these received signals. The signals undergoing thesepredetermined processes are demultiplexed by the demultiplexing unit 132into the pilot signal, the control information signal and the datasignal. The pilot signal is transferred to the channel estimating unit141, the control information signal is transferred to the demodulationunit 136, and the data signal is transferred to the demodulation unit133.

The channel estimating unit 141 compares the pilot signal transferredfrom the demultiplexing unit 132 with the already-known pilot signal,thereby obtaining a channel estimation value related to the downlink tothe mobile station 501 from the base station 500. The present inventiondoes not restrict this channel estimating method, and therefore thechannel estimation value may also be obtained from, e.g., thecalculation by the least-squares method. This channel estimation valueis transferred to the demodulation units 133 and 136 and the CQIinformation generation unit 143.

The CQI information generation unit 143 generates the CQI on the basisof the channel estimation value etc transferred from the channelestimating unit 141. The generation method by the CQI informationgeneration unit 143 is the same as by the CQI information generationunit 125 in the base station device, and hence its explanation is hereinomitted.

The demodulation unit 136 demodulates the control information signaltransferred from the demultiplexing unit 132 on the basis of the channelestimation value transferred from the channel estimating unit 141.Further, the demodulation unit 136 demodulates the control informationsignal by the demodulation method corresponding to the modulation method(QPSK) implemented by the base station 500 with respect to the controlinformation signal. This demodulation method involves utilizing themethod fixed in the system as the base station 500 retains thecorresponding modulation method by way of the fixed-in-system method.The demodulated control information signal is transferred to the controlinformation decoding unit 137.

The control information decoding unit 137 decodes the controlinformation signal transferred from the demodulation unit 136 by thedecoding method corresponding to the coding rate (⅓) and the codingmethod (the convolutional coding method) implemented by the base station500 with respect to the control information signal. This decoding methodinvolves utilizing the method fixed in the system as the base station500 retains the corresponding coding rate and coding method by way ofthe fixed-in-system method. The decoded control information data is sentto the error detection unit 139 and to the control information selectingunit 138.

The error detection unit 139 detects an error by checking the CRCallocated to the control channel. The error detection unit 139 sends adetection result to the control information selecting unit 138.

The control information selecting unit 138 selects the controlinformation used for the demodulation of the data channel in accordancewith the detection result sent from the error detection unit 139. Thecontrol information selecting unit 138, if the detection result shows noerror (normal), acquires the control information part 1 and the controlinformation part 2 in the control information data sent from the controlinformation decoding unit 137. The modulation method in the controlinformation part 1 is transferred to the demodulation unit 133, and thecoding rate in the control information part 1 is transferred to the datadecoding unit 134. The control information part 2 is transferred as itis to the data decoding unit 134. Whereas if the detection results showsoccurrence of the error, the control information selecting unit 138sends the control information part 1 estimated by the controlinformation estimating unit 142 respectively to the demodulation unit133 and to the data decoding unit 134, and notifies the data decodingunit 134 of the occurrence of the error.

The control information estimating unit 142 estimates the controlinformation part 1 on the basis of the SINR contained in the CQI givenfrom the CQI information generation unit 143. The control informationpart 1 is, as described above, the information generated in the basestation 500 on the basis of the SINR that is fed back from the mobilestation 501, and can therefore be generated in the mobile station 501 aswell. Namely, the control information estimating unit 142 previouslyretains the MCS table as shown in FIG. 6 and determines the coding rateand the modulation method by referring to this MCS table. The controlinformation part 1 is obtained by employing the thus-determined codingrate and modulation method. The thus-estimated control information part1 is sent to the control information selecting unit 138.

the demodulation unit 133 demodulates the data signal transferred fromthe demultiplexing unit 132 on the basis of the channel estimation valuetransferred from the channel estimating unit 141. The demodulation unit133 further demodulates this demodulated data signal by the demodulationmethod corresponding to the modulation method received from the controlinformation selecting unit 138. The demodulated data is sent to the datadecoding unit 134.

The data decoding unit 134 decodes the demodulated data on the basis ofthe coding rate and the coding method received from the controlinformation selecting unit 138. The decoded data is transferred to theerror detection unit 135. Moreover, the data decoding unit 134 extractsthe in-band information allocated to the head of the decoded data. Thedata decoding unit 134, if the [presence] is set in the presence/absenceinformation field of this in-band information, extracts the controlinformation part 2 from the decoded data on the basis of the location(address) information set in the same location information field. Thedata decoding unit 134, based on the error detection result of which theerror detection unit 135 has notified, if this detection result shows noerror (normal), outputs the decoded user data to other functional units(unillustrated), and sends the control information part 2 to the uplinktransmission frame generation unit 148.

Note that as for this control information part 2, if the informationshowing [absence] is set in the presence/absence information field ofthe in-band information, the control information part 2 received fromthe control information selecting unit 138 may be sent to the uplinktransmission frame generation unit 148, and, if the information showing[presence] is set in the presence/absence information field of thein-band information, the control information part 2 extracted by thedata decoding unit 134 may also be sent.

The error detection unit 135 detects the error by checking the CRC withrespect to the decoded data. This error detection result is fed back tothe data decoding unit 134.

The uplink transmission frame generation unit 148 sets, as the controlinformation, the control information part 2 received from the datadecoding unit 134 and the CQI information received from the CQIinformation generation unit 143, and generates a transmission frame fromthis control information and from the user data received from otherfunctional units (unillustrated). At this time, the uplink transmissionframe generation unit 148 encodes the control information at thepredetermined coding rate (⅓) and by the predetermined coding method(convolutional coding), and modulates the coded control information bythe fixed-in-system modulation method (QPSK). Further, the user dataundergoes the predetermined coding at the coding rate contained in thecontrol information part 2 received from the data decoding unit 134, andis modulated by the modulation method contained in the same controlinformation part 2. The thus-generated uplink transmission frame issubjected to the processes such as the digital/analog conversion and thefrequency conversion and is transmitted from the transmitting antenna150.

Operational Example

Operations of the base station 500 and the mobile stations 501 and 502in the first embodiment will hereinafter be explained. To start with,the transmitting operation of the base station 500 in the firstembodiment will be explained with reference to FIG. 5.

The base station 500, when transmitting the data to the mobile station501, transmits the data without conducting the in-band of the controlinformation part 2. This is because the data structuring unit 105determines not to allocate the control information part 2 to the datachannel, since the coding rate of the data channel regarding thetransmitted wireless frame that is determined by the rate determiningunit 123 does not get lower than the coding rate of the control channelthat is fixed in the system.

On the other hand, the base station 500, on the occasion of transmittingthe data to the mobile station 502, transmits the data conducted thein-band of the control information part 2. In this case, a CQI value ofwhich the mobile station 502 notifies is very poor quality, and thecoding rate of the data channel, which is determined by the ratedetermining unit 123, becomes lower than the fixed-in-system coding rateof the control channel. This being the case, the data structuring unit105 allocates the control information part 2 to the data channel.

Next, a receiving operation of each of the mobile stations 501 and 502in the first embodiment will be explained with reference to FIG. 8. FIG.8 is a flowchart showing an example of the receiving operation of eachof the mobile stations 501 and 502 in the first embodiment.

The demultiplexing unit 132, upon receiving the received signals fromthe reception unit 131, demultiplexes these received signals into thepilot signal, the control information signal and the data signal. Thechannel estimating unit 141 estimates the channel between the basestation and the mobile station from the thus-demultiplexed pilot signal(S801). The thus-estimated channel estimation value is sent to thedemodulation unit 136 related to the control information signal, and thecontrol information signal is demodulated based on the channelestimation value by the demodulation unit 136. Further, the demodulationunit 136 demodulates the control information signal by the demodulationmethod corresponding to the modulation method (QPSK) implemented by thebase station 500 (S802). Still further, the control information decodingunit 137 decodes the thus-demodulated control information data by thedecoding method corresponding to the coding rate (⅓) and the codingmethod (convolutional coding) implemented by the base station 500(S802).

The decoded control information data is sent to the error detection unit139, wherein the CRC is checked by the error detection unit 139. As aresult, if judged to have no error (S803; YES), the control informationselecting unit 138 transfers the control information part 1 contained inthe control information data to the demodulation unit 133 and to thedata decoding unit 134. The demodulation unit 133 demodulates the datasignal sent from the demultiplexing unit 132 on the basis of the channelestimation value given from the channel estimating unit 141, and furtherdemodulates the data signal by the demodulation method corresponding tothe modulation method contained in the control information part 1received from the control information selecting unit 138 (S804). Notethat at this time, the control information selecting unit 138, when thecontrol information part 2 is allocated to the control channel, extractsand transfers this control information part 2 to the data decoding unit134.

While on the other hand, if the error detection unit 139 judges thatthere is an error (S803; NO), the control information estimating unit142 estimates the modulation method and the coding rate from the CQI(SINR) given from the CQI information generation unit 143 (S805). Anestimation method by this control information estimating unit 142 is thesame as the determination method of determining the modulation methodand the coding rate by the rate determining unit 123 of the base station500. This estimated modulation method is sent to the demodulation unit133, while the estimated coding rate is sent to the data decoding unit134. With this operation, if the error occurs in the control channel,the demodulation unit 133 demodulates the data by the modulation methodestimated by the control information estimating unit 142 (S806).

The data decoding unit 134, if the error occurs in the control channel,executes predetermined decoding corresponding to the coding rateestimated by the control information estimating unit 142, and, if theerror does not occur in the control channel, executes predetermineddecoding corresponding to the coding rate set in the control informationpart 1 of the control channel (S807). The decoded CRC is checked by theerror detection unit 135, thereby checking whether or not the erroroccurs in the data allocated to the data channel. Then, if judged tohave the error in the data (S808; NO), a retransmission request is made.

The data decoding unit 134, if judged to have no error from theinformation, showing whether or not the error occurs in the controlchannel, of which the control information selecting unit 138 hasnotified (S809; YES), sends the control information part 2 in thecontrol channel to the uplink transmission frame generation unit 148.Whereas if judged to have the error (S809; NO) and if the in-band isconducted (S810; YES), the data decoding unit 134 sends the controlinformation part 2 allocated (in-band) into the data channel to theuplink transmission frame generation unit 148 (S811). Note that if theerror occurs in the control channel (S809; NO) and if the in-band is notconducted (S810; NO), the retransmission request is made.

Operation and Effect in Embodiment

The wireless communication system in the first embodiment involvesemploying the frame format, wherein the control information, whichshould be originally transmitted by the control channel, is segmentedinto the control information part 1 consisting of the downlink controlinformation and into the control information part 2 consisting of theuplink control information, and the control information part 2 is duallyallocated to the control channel and to the data channel.

In the base station 500, the data structuring unit 105 compares the datachannel coding rate determined by the rate determining unit 123 with thefixed-in-system coding rate of the control channel, and thus determineswhether or not the control information part 2 is allocated (in-band)into the data channel. The rate determining unit 123 determines thecoding rate etc of the data channel, corresponding to the channel status(CQI) with the mobile station as the transmission destination. Then, inthe case of transmitting to the mobile station that is located in thevicinity of the base station 500 and in a good channel status as themobile station 501 is, the wireless frame format without conducting thein-band of the control information part 2 is used. On the other hand, inthe case of transmitting to the mobile station that is located at thecell edge and in a channel status of very poor quality as the mobilestation 502 is, the wireless frame format with conducting the in-band ofthe control information part 2 is used.

Thus, in the first embodiment, the determination is made correspondingto the channel status with the mobile station as the transmissiondestination so as not to conduct the in-band in the case of thepreferable channel status (the case where the coding rate of the datachannel does not become lower than the coding rate of the controlchannel) and so as to conduct the in-band in the case of the poorchannel status (the case where the coding rate of the data channel getslower than the coding rate of the control channel).

The use of this type of frame format, according to the first embodiment,eliminates the necessity of increasing the size of the control channeland does not cause an extreme rise in the overhead of the transmissionframe.

In the mobile station, the control information signal in the controlchannel is demodulated and decoded by the fixed-in-system demodulationmethod, coding rate and decoding method. The demodulated and decodedcontrol information data is checked the CRC by the error detection unit139, thereby checking whether or not the error exists in the controlinformation data. Herein, if judged to have the error, the controlinformation data can not be used, and hence the control informationestimating unit 142 estimates the modulation method and the coding rateon the basis of the CQI generated by the CQI information generation unit143. Hereafter, the data in the data channel is, if no error exists inthe control channel, demodulated and decoded based on the controlinformation in the control channel, and is, if the error exists in thecontrol channel, demodulated and decoded by the modulation method, thecoding rate and the decoding method that are estimated by the controlinformation estimating unit 142.

Thus, in the first embodiment, even when the error occurs in the data inthe control channel, the control information, which should be allocatedto the control channel concerned, is estimated by the same method as thegeneration method of the base station 500 as a generator of the controlinformation, and the data channel is demodulated and decoded by use ofthe thus-estimated control information.

Accordingly, if the error occurs in the control channel, there was noalternative but to prompt the retransmission to be done, however,according to the first embodiment, the data channel can be demodulatedand decoded based on the equal control information, thereby eliminatingthe necessity of prompting the retransmission to be done. With thiseffect, even when the error frequently occurs in the control channel inthe communications with the mobile station located at the cell edge, itis possible to avoid a phenomenon of causing a decrease in transmissionefficiency of the system as a whole by repeating the retransmission.

Further, in the mobile station, if the error occurs in the controlchannel and when the control information part 2 is allocated (in-band)into the data channel, the uplink transmission frame is generated basedon the control information part 2 in the data channel.

Thus, in the first embodiment, even if originally unable to acquire theuplink control information contained in the control information due tothe occurrence of the error in the control channel, the uplinktransmission control information is allocated (in-band) into the datachannel, and therefore the frame for the uplink transmission isgenerated by use of the uplink transmission control informationconducted the in-band.

Accordingly, this configuration also enables a retransmission requestfrequency to be decreased and, more essentially, a throughput of thewhole system to be improved.

Second Embodiment

The wireless communication system according to a second embodiment ofthe present invention will hereinafter be described. The wirelesscommunication system according to the first embodiment discussed aboveuses the frame format corresponding to the example shown in FIG. 1 asdiscussed in the item of Outline of Embodiments of the Invention, i.e.,the frame format having the structure in which the control informationpart 2 is dually allocated to the control channel (CCH) and to the datachannel (DCH). The wireless communication system in the secondembodiment uses the frame format corresponding to the exampleillustrated in FIG. 2 discussed in the item of Outline of Embodiments ofthe Invention. The description shall be focused on different functionalunits from those in the first embodiment with respect to the basestation 500 and the mobile stations 501, 502 that configure the wirelesscommunication system in the second embodiment. A configuration in thesecond embodiment in the following discussion is an exemplification, andthe present invention is not limited to the following configuration.Note that the system architecture is the same as in the case of thefirst embodiment, and hence its explanation is omitted.

Frame Format

The frame format used in the wireless communication system in the secondembodiment will be described with reference to FIGS. 9 and 10. FIGS. 9and 10 are diagrams each showing the frame format in the secondembodiment, and illustrating the format of the frame (the downlinkframe) transmitted from the base station 500 to the mobile station 501or 502. The frame format in the second embodiment corresponds to theexample shown in FIG. 2 discussed in the item of Outline of Embodimentsof the Invention, and has a structure in which the control informationpart 2 is allocated to only the data channel (DCH). FIG. 9 shows theframe format in a case where the in-band is not conducted, and FIG. 10shows the frame format in a case where the in-band is conducted.

The segmentation method of the control information in the secondembodiment shall be the same as that in the first embodiment. Namely,the downlink control information is defined as the control informationpart 1 (PART 1), and the uplink control information is defined as thecontrol information part 2 (PART 2). Further, the detailed informationcontained in the uplink control information and the detailed informationcontained in the downlink control information are the same as those inthe first embodiment.

In the frame format in the second embodiment, a header channel (HCH) isattached. The header channel contains the in-band information and theCRC. The in-band information contains the presence/absence informationshowing whether the control information part 2 is allocated (in-band) inthe data channel or not and the allocation information showing alocation where the control information part 2 in the data channel isallocated. A piece of identifying information showing [presence] in thecase of conducting the in-band is set in the presence/absenceinformation field, and the identifying formation showing [absence] inthe case of conducting none of the in-band is set in thepresence/absence information field. A piece of information showing, inthe case of conducting the in-band, an in-band location of the controlinformation part 2 in the data channel, is set in the allocationinformation field. A CRC bit related to the data contained in the headerchannel is set in the CRC field.

In the frame format in the case of conducting none of the in-band shownin FIG. 9, both of the control information part 1 and the controlinformation part 2 are allocated to the control channel, and only theuser data is allocated to the data channel. On the other hand, in theframe format in the case of conducting the in-band shown in FIG. 10, thecontrol information part 1 is allocated to the control channel, whilethe control information part 2 is allocated to the data channel. In thiscase, the user data and the control information part 2 are eachallocated to the data channel.

Base Station

A device configuration of the base station 500 in the second embodimentwill hereinafter be described with reference to FIG. 11. FIG. 11 is ablock diagram showing the device configuration related to thetransmitting functions of the base station 500 in the second embodiment.The base station 500 in the second embodiment includes, as thetransmitting functions, in addition to the configuration in the firstembodiment, a header generation unit 171 and a modulation unit 172. Asthe functional units other than these units, the functions related tothe data structuring unit 105 and the multiplexing unit 109 are changed,and hence these units are exclusively explained, while the remainingfunctional units are the same as those in the first embodiment and aretherefore omitted in their explanations.

The data structuring unit 105 generates the data that is allocated tothe data channel in the frame format shown in FIG. 9 or 10. Here at, thedata structuring unit 105 compares the coding rate of the data channelthat is received from the rate determining unit 123 with thefixed-in-system coding rate of the control channel, and thus determineswhether the control information part 2 received from the controlinformation part 2 generation unit 103 is conducted the in-band or not.Specifically, the data structuring unit 105, if the coding rate of thedata channel is lower than the coding rate of the control channel,allocates the control information part 2 to a predetermined location inthe data channel but does not allocate the control information part 2into the data channel in cases other than this. The data structuringunit 105, in the case of conducting the in-band of the controlinformation part 2, notifies the header generation unit 171 of a purportthat the in-band is conducted and of a location (an offset address etc)of the control information part 2.

The header generation unit 171 generates, based on the notificationgiven from the data structuring unit 105, the in-band information dataand the CRC data that are allocated to the header channel. The headergeneration unit 171, with respect to the in-band information data, setsthe presence or absence of the in-band, of which the data structuringunit 105 has notified, in the presence/absence information field, andsets the similarly-notified location of the control information part 2in the allocation information field, thereby generating the in-bandinformation data. Then, the header generation unit 171 generates the CRCbit on the basis of the thus-generated in-band information data.

The header generation unit 171 encodes the thus-generated data by thepredetermined coding rate. The coding rate and the coding methodimplemented by this header generation unit 171 involve using thefixed-in-system coding rate and coding method, wherein, for example, theconvolutional coding method having the coding rate ⅓ is used. The codeddata is subjected to the predetermined modulation process by themodulation unit 172 and is transferred to the multiplexing unit 109. Themodulation method implemented by the modulation unit 172 also involvesusing the fixed-in-system method, wherein, for instance, the QPSK isused. Note that the coding rate, the coding method and the modulationmethod concerning the header channel involve employing thefixed-in-system methods and may also be retained adjustably in a tableand so on. Moreover, the present invention does not limit the codingrate, the coding method and the modulation method related to the headerchannel.

The multiplexing unit 109 multiplexes each of the modulated pilotsignal, control information signal, data signal and header signal, andtransfers these multiplexed signals to the transmission unit 110. Themultiplexed signals transferred to the transmission unit 110 undergo theprocesses such as the digital/analog conversion and the frequencyconversion, and are transmitted from the transmitting antenna 115.

Mobile Station

A device configuration of each of the mobile stations 501 and 502 in thesecond embodiment will hereinafter be described with reference to FIG.12. FIG. 12 is a block diagram showing the device configuration relatedto the receiving functions of the mobile stations 501 and 502 in thesecond embodiment. Note that the mobile stations 501 and 502 are eachthe same device, and hence the following discussion shall deal with themobile station 501. The mobile station 501 in the second embodimentincludes, as the receiving functions, in addition to the configurationin the first embodiment, a demodulation unit 181 and a header decodingunit 182. As the functional units other than these units, the functionsrelated to the demultiplexing unit 132, the control informationselecting unit 138 and the data decoding unit 134 are changed, and hencethese units are exclusively explained, while the remaining functionalunits are the same as those in the first embodiment and are thereforeomitted in their explanations.

The demultiplexing unit 132, upon receiving the received signals fromthe reception unit 131, at first demultiplexes the header signal and thepilot signal therefrom. The demultiplexed pilot signal is transferred tothe channel estimating unit 141. The header signal is transferred to thedemodulation unit 181. The demultiplexing unit 132, when receiving thedecoded data from the header decoding unit 182, refers to the in-bandinformation in the received data, thereby judging the presence orabsence of the in-band. To be specific, the demultiplexing unit 132,when the identifying information showing [presence] is set in thepresence/absence information field in the in-band information, judgesthat the in-band is set, and further acquires the location informationof the control information part 2 set in the allocation informationfield. Conversely, the demultiplexing unit 132, when the identifyinginformation showing [absence] is set in the presence/absence informationfield in the in-band information, judges that the in-band is notconducting.

In the second embodiment, the sizes of the control channel and of thedata channel change depending on the presence of the in-band (see FIGS.9 and 10), and therefore the demultiplexing unit 132 demultiplexes thecontrol channel and the data channel in accordance with a result of thejudgment as to the presence of the in-band. The demultiplexed controlinformation signal is transmitted together with the in-band informationto the demodulation unit 133.

The demodulation unit 181 demodulates the header signal transferred fromthe demultiplexing unit 132 on the basis of the channel estimation valuetransferred from the channel estimating unit 141. Moreover, thedemodulation unit 181 demodulates the header signal by the demodulationmethod corresponding to the modulation method (QPSK) implemented by thebase station 500. This demodulation method involves utilizing thefixed-in-system method as the corresponding modulation method isretained as the fixed-in-system method in the base station 500. Thedemodulated header signal is transferred to the header decoding unit182.

The header decoding unit 182 decodes the header signal transferred fromthe demodulation unit 181 by the decoding method corresponding to thecoding rate (⅓) and the coding method (convolutional coding method)implemented by the base station 500 with respect to the header signal.This decoding method involves utilizing the fixed-in-system method asthe corresponding coding rate and the corresponding coding method areretained as the fixed-in-system method in the base station 500. Thedecoded pieces of data, i.e., the in-band information and the CRC aresent to the demultiplexing unit 132.

The control information selecting unit 138 receiving the in-bandinformation via the demodulation unit 136 and via the controlinformation decoding unit 137 from the demultiplexing unit 132, selectsthe control information used for the demodulation of the data channel,corresponding to this in-band information and to a detection result sentfrom the error detection unit 139. The control information selectingunit 138, when the [presence] is set in the presence/absence informationfield in the in-band information and when the detection result shows noerror, sends the modulation method in the control information part 1transmitted from the control information decoding unit 137 to thedemodulation unit 133, and sends the coding rate therein to the datadecoding unit 134. The control information selecting unit 138, when the[absence] is set in the presence/absence information field in thein-band information and when the detection result shows no error(normal), acquires respectively the control information part 1 and thecontrol information part 2 in the control information data sent from thecontrol information decoding unit 137. The modulation method in thecontrol information part 1 is sent to the demodulation unit 133, thecoding rate therein is sent to the data decoding unit 134, and thecontrol information part 2 is sent as it is to the data decoding unit134. Further, when the [presence] is set in the presence/absenceinformation field in the in-band information and when the detectionresult shows the error occurrence, the control information selectingunit 138 sends the control information part 1 estimated by the controlinformation estimating unit 142 to the demodulation unit 133 and to thedata decoding unit 134, respectively. When the [absence] is set in thepresence/absence information field in the in-band information and whenthe detection result shows the error occurrence, the control informationselecting unit 138 specifies a process of a request for theretransmission (unillustrated).

The data decoding unit 134 decodes the demodulated data on the basis ofthe coding rate and the coding method received from the controlinformation selecting unit 138. The decoded data is transferred to theerror detection unit 135. Further, the data decoding unit 134 extractsthe control information part 2 from the decoded data on the basis of thein-band information transferred via the demodulation unit 133 from thedemultiplexing unit 132. To be specific, the data decoding unit 134, ifthe identifying information showing the [presence] is set in thepresence/absence information field in the in-band information, extractsthe control information part 2 from the decoded data on the basis of thelocation (address) set in the same allocation information field. Thedata decoding unit 134, based on the error detection result of which theerror detection unit 135 has notified, if this detection result shows noerror (normal), outputs the decoded user data to other functional units(unillustrated), and sends the control information part 2 to the uplinktransmission frame generation unit 148. Further, the data decoding unit134, if the identifying information showing the [absence] is set in thepresence/absence information field in the in-band information and if theerror detection result of which the error detection unit 135 hasnotified shows no error (normal), outputs the decoded user data to otherfunctional units (unillustrated), and sends the control information part2 transmitted from the control information selecting unit 138 to theuplink transmission frame generation unit 148.

Operational Example

Operations of the base station 500 and the mobile stations 501, 502 inthe second embodiment will hereinafter be described. To begin with, thetransmitting operation of the base station 500 in the second embodimentwill be explained with reference to FIG. 11.

The base station 500, when transmitting the data to the mobile station501, transmits the data without conducting the in-band of the controlinformation part 2. This is because the data structuring unit 105determines not to allocate the control information part 2 to the datachannel, since the coding rate of the data channel regarding thetransmitted wireless frame that is determined by the rate determiningunit 123 does not get lower than the fixed-in-system coding rate of thecontrol channel. In this case, the information showing the [absence] isset in the presence/absence information field in the in-band informationgenerated by the header generation unit 171.

On the other hand, the base station 500, on the occasion of transmittingthe data to the mobile station 502, transmits the data conducted thein-band of the control information part 2. In this case, a CQI value ofwhich the mobile station 502 notifies is very poor quality, and thecoding rate of the data channel, which is determined by the ratedetermining unit 123, becomes lower than the fixed-in-system coding rateof the control channel. This being the case, the data structuring unit105 allocates the control information part 2 to the data channel. Inthis case, the information showing the [presence] is set in thepresence/absence information field in the in-band information generatedby the header generation unit 171, and the location information of thecontrol information part 2 in the data channel is set in the allocationinformation field.

Next, a receiving operation of each of the mobile stations 501 and 502in the second embodiment will be explained with reference to FIGS. 12and 13. FIG. 13 is a flowchart showing an example of the receivingoperation of each of the mobile stations 501 and 502 in the secondembodiment.

The demultiplexing unit 132, upon receiving the received signals fromthe reception unit 131, demultiplexes the pilot signal and the headersignal from these received signals. The channel estimating unit 141estimates the channel between the base station and the mobile stationfrom the thus-demultiplexed pilot signal (S1301). The thus-estimatedchannel estimation value is sent to the demodulation unit 181 related tothe header signal, and the header signal is demodulated based on thechannel estimation value by the demodulation unit 181. Further, thedemodulation unit 181 demodulates the header signal by the demodulationmethod corresponding to the modulation method (QPSK) implemented by thebase station 500 (S1302). Still further, the header decoding unit 182decodes the thus-demodulated header data by the decoding methodcorresponding to the coding rate (⅓) and the coding method(convolutional coding) implemented by the base station 500 (S1302).

The demultiplexing unit 132 checks the decoded CRC allocated to theheader channel and thus judges whether the error occurs in the headerchannel or not. Herein, if the error exists in the header channel(S1303; NO), the processing is terminated. Whereas if no error exists inthe header channel (S1303; YES), the demultiplexing unit 132 grasps,based on the in-band information transferred from the header decodingunit 182, whether the in-band of the control information part 2 isconducted or not, and demultiplexes the control signal and the datasignal from the receiving signals.

The demodulation unit 136 demodulates the demultiplexed control signalon the basis of the channel estimation value. Further, the demodulationunit 136 demodulates the control information signal by the demodulationmethod corresponding to the modulation method (QPSK) implemented by thebase station 500 (S1304). Still further, the control informationdecoding unit 137 decodes the demodulated control information data bythe decoding method corresponding to the coding rate (⅓) and the codingmethod (convolutional coding) implemented by the base station 500(S1304).

The decoded control information data is sent to the error detection unit139 and is CRC-checked by the error detection unit 139. As a result, ifjudged to have no error (S1305; YES), the control information selectingunit 138 transfers the control information part 1 contained in thecontrol information data to the demodulation unit 133 and to the datadecoding unit 134. The demodulation unit 133 demodulates the data signalgiven from the demultiplexing unit 132 on the basis of the channelestimation value given from the channel estimating unit 141, and furtherdemodulates the data signal by the demodulation method corresponding tothe modulation method contained in the control information part 1received from the control information selecting unit 138 (S1306). Notethat at this time, the control information selecting unit 138, if thecontrol information part 2 is allocated in the control channel, extractsand transfers this control information part 2 to the data decoding unit134.

Whereas if the error detection unit 139 judges that the error exists(S1305; NO), the control information estimating unit 142 estimates themodulation method and the coding rate from the CQI (SINR) given from theCQI information generation unit 143 (S1307). The estimating method bythis control information estimating unit 142 is the same as thedetermination method of determining the modulation method and the codingrate by the rate determination unit 123 in the base station 500. Thisestimated modulation method is sent to the demodulation unit 133, andthe estimated coding rate is sent to the data decoding unit 134. Withthis operation, if the error occurs in the control channel, thedemodulation unit 133 demodulates the data by the modulation methodestimated by the control information estimating unit 142 (S1308).

The data decoding unit 134, if the error occurs in the control channel,executes the predetermined decoding corresponding to the coding rateestimated by the control information estimating unit 142, and, whereasif the error does not occur in the control channel, executes thepredetermined decoding corresponding to the coding rate set in thecontrol information part 1 of the control channel (S1309). The errordetection unit 135 checks the decoded CRC, thereby checking whether ornot the error occurs in the data allocated to the data channel. Then, ifjudged to have the error (S1310; NO), the retransmission request ismade.

The data decoding unit 134, if judged to have no error from theinformation showing whether or not the error occurs in the controlchannel of which the control information selecting unit 138 has notified(S1311; YES), sends the control information part 2 in the controlchannel to the uplink transmission frame generation unit 148. Whereas ifjudged to have the error (S1311; NO) and if the in-band is conducted(S1312; YES), the data decoding unit 134 sends the control informationpart 2 allocated (in-band) to the data channel of the uplinktransmission frame generation unit 148 (S1313). Note that if judged tohave the error in the control channel (S1311; NO) and if the in-band isnot conducted (S1312; NO), the retransmission request is made.

Operation and Effect in Embodiment

In the wireless communication system in the second embodiment, the caseof conducting the in-band involves employing the frame format in whichthe control information part 2 is allocated to only the data channel.Corresponding to this frame format, in the frame in the secondembodiment, the header channel containing the in-band information isattached. This is because the size of the control channel in this frameformat is variable depending on the case of conducting the in-band andthe case of conducting none of the in-band.

With this operation, the mobile station receiving the frame can judgethe presence or absence of the in-band simply by referring to thein-band information in this header channel. Further, the attachedin-band information after all contains nothing but the presence/absenceinformation and the allocation information, and therefore the overheadof the transmission frame does not extremely increase.

Further, when transmitting to the mobile station in the channel statusthat is as bad as requiring the in-band, the uplink control informationis allocated to the data channel, and hence the size of the controlchannel can be reduced. This, according to the second embodiment,enables the overhead of the transmission frame to be reduced.

1. A wireless communication device performing communications by using aradio frame containing a control channel and a data channel, thewireless communication device comprising: a structuring unit thatallocates a first part of the control channel adjacent to the datachannel in the radio frame, and allocates a second part of the controlchannel, which denotes different control information from the firstpart, to the data channel so as to be inserted between data of the datachannel; and a transmission unit that transmits the radio frameincluding the data channel and the control channel.
 2. The wirelesscommunication device according to claim 1, wherein the first part of thecontrol channel denotes control information relating to result of errordetection for received signal, and the second part of the controlchannel denotes a channel quality indicator.
 3. A method for a wirelesscommunication device performing communications by using a radio framecontaining a control channel and a data channel, the method comprising:allocating a first part of the control channel adjacent to the datachannel in the radio frame, and allocating a second part of the controlchannel, which denotes different control information from the firstpart, to the data channel so as to be inserted between data of the datachannel.